A specialist mimic of a specialist butterfly

Both the Baltimore and Harris' checkerspots have gregarious specialist caterpillars which mimic each other but feed on totally different host plants. They even create extremely similar larval aggregation webs. The presence of this cluster being on white aster, and slight differences in color patterns keys this one out to Harris' checkerspot (Closyne harrisii). They're feeding fast before going into a late summer diapause.